This article examines the effects of changes in family structure (from a family with two original parents to a lone-parent family or a stepfamily) on emotional-behavioral and cognitive outcomes of young children. We use data from three cycles of the National Longitudinal Surveys of Children and Youth, first conducted in 1994-95, and every 2 years since then. The present analysis is based on data for children, who were 4 to 7 years old at the first cycle. We find that compared with children in families with two original parents, those in lone-parent and stepparent families are at a disadvantage on every measure of child outcome, even when their initial disadvantages and socioeconomic background are taken into account. We also find that the deterioration in economic resources is more important in explaining the relationship between family structure and cognitive outcomes (such as math and reading scores) but not emotional-behavioral outcomes, whereas the deterioration in familial resources ? ineffective parenting and parental depression, in particular ? is more important in explaining the effects on emotional-behavioral outcomes. The scarcity of material resources mediates the relationship between family structure and cognitive outcomes, whereas the diminution of familial resources mediates the relationship between changes in family structure and emotional-behavioral outcomes. [ABSTRACT FROM AUTHOR]